1. Field of the Invention
The present invention relates to an electrical cable, for communication purposes, having at least two spaced-apart, insulated electrical conductor means, between each two of which is disposed a portion having a block-shaped cross-section, with a plurality of tension-absorbing elements of high-strength fibers being disposed in each of these portions; the insulation of the conductor means, and the portion for the tension-absorbing elements, are formed by a connecting casing of thermoplastic or elastomeric material in which the conductor means and the tension-absorbing elements are embedded in such a way that they are essentially oriented in the longitudinal direction of the cable parallel to one another; provided between a given one of the portions for the tension-absorbing elements, and an adjoining casing of a conductor means, are longitudinally extending separating grooves, so that the cable has an at least three-part cross-sectional shape.
2. Description of the Prior Art
A cable of this general type is known from U.S. Pat. No. 4,220,812--Ney et al., issued Sept. 2, 1980 to the assignee of the present application. In this known cable, the tension-absorbing elements are symmetrically disposed in pairs in the block-shaped central portion of the cable; this is supposed to produce a uniform flexibility in the two main directions of the cable. The bending axis apparently coincides with the imaginary connecting line between the electrical conductors. This also leads to a symmetrical configuration of the entire cable cross-section.
Similar electrical cables having symmetrical cross-sectional shapes are shown in U.S. Pat. Nos. 2,950,338 (Taylor), 2,628,998 (Frisbie), 2,663,755 (McBride), 3,060,260 (Scofield), 3,458,650 (Miyawaki et al), 3,549,788 (Apen et al), 3,927,248 (Scholl), and the aforementioned U.S. Pat. No. 4,220,812 (Ney et al); in the Canadian Pat. No. 481,628 (Witthoft); in the British Pat. No. 414,713 (Pirelli); in the French Patent application No. 22 74 123 (Thomson-Brandt); in German Offenlegungsschrift No. 23 06 386 (Kubelwerk Wagner); and in German Auslegeschrift No. 10 04 253 (Hohn).
Most of these heretofore known cables contain only a single load-carrying element or tension-absorbing element in the form of a thin, flexible steel cable which is encased with the same material as is the electrical conductor of the cable. Cables of this type are also known which have two stranded wires embedded in the casing. Only the aforementioned U.S. Pat. No. 4,220,812 (Ney) has a greater number of tension-absorbing elements, with these elements comprising fibers of glass or graphite. With all of the heretofore known cables, the bending property is uniform at right angles to the longitudinal central plane of the cable due to its symmetrical configuration. However, as a result these known cables cannot always satisfy certain requirements when the cables are being laid. Although the bending is well controlled when the cable is suspended between poles or buildings, the small bending radii required in conjunction with termination of the wire can often not be achieved, or lead to damage of the cable, which initially cannot even be recognized. The bending properties are also significant with regard to connecting the cables. The requirements cannot be optimally fulfilled with the heretofore known constructions.
An object of the present invention is to provide an electrical cable of the aforementioned general type which has selected bending properties with which it can conform to the particular requirements for termination and connection without adversely affecting the tensile strength of the cable in the field of termination for example when rigged between poles. In other words, the flexibility of the cable is to be improved by structural measures. In so doing, the cable should be capable of being produced in a simple manner without significant alteration of the customary manufacturing equipment.